JPH058468U - Crossed coil instrument - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a cross-coil type instrument capable of reducing heat generation, suppressing occurrence of needle jumping phenomenon and needle clogging phenomenon, and reducing mechanical hysteresis. A signal processing is performed based on an input signal that changes according to a measured amount, and two types of drive signals having a predetermined phase difference from each other are cross-arranged at a predetermined angle. In the cross-coil type instrument for supplying the coils 31 and 32, the power supply voltage from the constant voltage circuit to the drive circuit is periodically switched to a low voltage.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a cross coil type instrument used as, for example, an engine tachometer of an automobile.

[0002]

[Prior Art]

 As shown in FIG. 5, a conventional cross-coil type instrument includes a frequency-control angle arithmetic circuit (abbreviated as input signal arithmetic circuit) 1, a drive signal arithmetic circuit 2, a drive circuit 3 and a cross coil type instrument unit 4. However, each of these will be described below.

First, the input signal calculation circuit 1 is composed of a cycle measuring circuit 11 and a control angle calculating circuit 12, and the cycle measuring circuit 11 is a frequency signal whose frequency changes in accordance with an amount to be measured such as an engine speed. The period fi is measured, and the input frequency f _i is obtained from the period (T). In addition, the control angle calculation circuit 12 uses the period measurement value (T 1 = 1 / f _i ) from the period measurement circuit 11 in the preceding stage as a movable magnet rotation control angle (hereinafter, abbreviated as a needle deflection angle) signal a (see FIG. 6A). ) And output.

The drive signal operation circuit 2 is composed of an approximate sine wave generation circuit 21, an approximate cosine wave generation circuit 22 and a polarity switching circuit 23, and the circuits 11, 12, 21, 22, 23 are constituted by, for example, a microcomputer. ing. The approximate sine wave generation circuit 21 and the approximate cosine wave generation circuit 22 both receive the pointer deflection angle signal a from the input signal calculation circuit 1, and based on the pointer deflection angle signal a, angle comparison, phase shift, etc. By performing the signal processing described above, the PWM signals b and c (see FIG. 6B) which have a phase difference of 90 ° with each other and which change in the characteristics of the pentagonal wave according to the angle value of the signal a are output. .. Further, the polarity switching circuit 23 polarizes the output signals b and c from the approximate sine wave generating circuit 21 and the approximate cosine wave generating circuit 22 on the basis of the signal a 1 to polarize switching signals d and e (Fig. (See 6 c).

The drive circuit 3 is composed of two output circuits 24 and 25, and each output circuit 24 and 25 is a bidirectional switch circuit composed of, for example, a transistor, and is the approximate sign wave generation circuit 21 and the approximate cosine. The output signals b and c from the wave generating circuit 22 are current-amplified, respectively, and the output signals b and c are polarized based on the polarity switching signals d and e to generate two types of drive signals f and g ( (See FIG. 6D). The cross-coil type instrument unit 4 is supplied with the two kinds of drive signals f and g from the drive circuit 2, and is paired with a pair of coils 31 and crossed with each other at an angle of 90 °. 32 and a movable magnet 33, which is rotatably arranged under the magnetic action of the pair of coils 31 and 32 and is magnetized by two poles.

In addition, 5 is a constant voltage power source for making the output voltage of the power source 6 constant, and a constant voltage of 5 V is applied to the signal processing circuit 2. Reference numeral 7 denotes a constant voltage power source that makes the output voltage of the power source 6 constant, and supplies and applies a constant voltage of 8 V to the drive circuit 3.

[0007]

[Problems to be solved by the device]

 However, in such a conventional cross-coil type meter, since there is hysteresis due to bearings, etc., in order to cancel it, a large constant voltage (8 V) is applied to the drive circuit 3 and crossing is performed via the current limiting resistor R. A predetermined current is applied to the coils 31 and 32 to drive the cross-coil type instrument unit 4 to forcibly display the correct indication value. As a result, the amount of heat generated in the low-voltage circuit 7, the current limiting resistor R, and the cross coil portion becomes large, and it is necessary to take heat dissipation measures, and there is the problem that a place for installing a heat sink must be secured. there were.

The present invention has been made in view of such conventional problems, and an object thereof is to reduce heat generation and more efficiently reduce hysteresis.

[0009]

[Means for Solving the Problems]

 The cross-coil type instrument according to the present invention rotatably disposes a movable magnet magnetized by two poles under the magnetic action of a pair of coils that are arranged to cross each other at a predetermined angle (for example, 90 °). The cross-coil type instrument unit and the two waveform generation circuits that input signals that change according to the quantity to be measured perform signal processing based on the signals (for example, angle comparison, phase shift, etc.). Two types of drive that have a predetermined phase difference (for example, an electrical angle of 90 °) with each other and that change according to the value of the signal (for example, characteristics such as a triangular wave, a trapezoidal wave, or a sine wave). In a cross-coil type instrument equipped with a drive circuit that outputs a signal and a constant voltage circuit that supplies power to the drive circuit, the power supply voltage from the constant voltage circuit to the drive circuit may be periodically switched to a low voltage. Configured in It

[0010]

[Action]

 As described above, by periodically switching the power supply voltage from the constant voltage circuit to the drive circuit to the low voltage or the high voltage, the amount of power supplied to the cross coil is reduced, and the amount of heat generation is reduced accordingly. Also, the amount of hysteresis reduction is greater than when a high pulsating voltage is applied by direct current by pulsating the cross coil applied voltage at a predetermined voltage.

[0011]

【Example】

 The invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the present invention. First, the configuration will be described. Here, reference numerals 1, 11, 12, 2, 21, 21 to 25, 3, 31 to 33 and symbols fi, a, b, c, d, f and g are conventional ones in FIGS. Same as the example, the same configuration is shown, and duplicated description is omitted.

Reference numeral 8 denotes a switching timing generation circuit, which periodically switches between high and low output voltage of the constant voltage power source 7 according to the switching timing from the circuit 8. This switching timing is created by the drive signal arithmetic circuit 2, and therefore the switching timing generation circuit 8 is provided in the drive signal arithmetic circuit 2.

FIG. 2 shows a specific configuration of the constant voltage power supply 7. A Zener diode ZD1 having a Zener voltage of 5V and a Zener voltage of 3V are provided on the base of a transistor T1 having a resistor R1 connected between a collector and a base. The zener diode ZD2 is connected in series, the transistor T2 is connected in parallel with the zener diode ZD2, and the switching timing signal Si is applied to the transistor T2 via the resistor R2.

Next, the operation of the configuration of this embodiment will be described based on the timing chart of FIG. 3 and the flowchart of FIG. 4, but the approximation of the input signal arithmetic circuit 1, the drive signal arithmetic circuit 2, and the drive circuit 3 will be described. The sine wave generation circuit 21, the approximate cosine wave generation circuit 22, and the polarity switching circuit 23 perform the same operation as the conventional example described in FIG. Drive signal operation circuit 2 and an input signal arithmetic circuit 1 in this embodiment is a microcomputer, periodically measures the input signal f _i, averaged, etc. data operation, the control angle terms, SI N, PWM value calculation COS, switching The period T of the timing signal Si and the pause width t are controlled to control the PWM output to the drive circuit 3 (steps ST4-1 to ST4-6).

When the switching timing signal Si shown in FIG. 3 in which the period T and the pause width t are controlled as described above is applied to the base of the transistor T2 of the constant voltage power supply 7, the switching timing signal Si is supplied in accordance with the switching timing signal Si. The transistor T2 turns on and off. As the transistor T2 is turned on and off, the output voltage Vo of the constant voltage power source 7 periodically changes to 5V and 8V as shown in FIG. The pulse width of the high voltage 8V is sufficient for several ms. Therefore, if the cycle is set to several tens Hz, the duty of 8V is several%.

As a result, the amount of power supplied from the drive circuit 3 to the cross coils 31, 32 current limiting resistance R is reduced, and the amount of heat generation can be reduced.

Further, in the cross coil type instrument, the approximate sine wave generating circuit 21 and the approximate cosine wave generating circuit 22 perform a signal processing such as an angle comparison and a phase shift of the DC voltage signal a and a characteristic of a pentagonal wave. The offset voltage of the operational amplifier, etc., which is provided to generate the PWM signals b and c that change with, cannot be made completely zero, so at the part marked with a circle in Fig. 6D, the needle jump phenomenon A (the pointer of the cross coil type instrument unit) Is a phenomenon in which the change rate is extremely larger than the normal input conversion rate), and there is a needle stop phenomenon B (the phenomenon in which the pointer of the cross coil type instrument unit does not follow the change in input) in the □ part. Occurs.

However, according to the present invention, the output signal of the drive circuit 3 is periodically changed as described above, so that there is a signal change such that a needle jump phenomenon or a needle stop phenomenon occurs due to the circuit configuration of the waveform generation circuit. Even if there is, the signal change is mixed in the ripple signal, which apparently eliminates the needle jump phenomenon and the needle stuck phenomenon. Further, since the applied voltage to the cross coil is pulsated, the driving torque is low at low voltage and high at high voltage, and vibration at the pulsating frequency is applied to the drive shaft, which reduces hysteresis.

[0019]

[Effect of the device]

 As described above, according to the present invention, the constant voltage circuit is configured to apply the power supply voltage having a cyclically different voltage value to the drive circuit that outputs the drive signal to the pair of cross coils. The amount of power supplied to the coil is reduced, and the amount of heat generated by the cross coil can be reduced.

Further, the output signal of the drive circuit periodically changes by being applied with a power supply voltage having a different voltage value periodically. As a result, it is possible to reduce the manufacturing variations of the drive circuit, the needle jumping due to temperature and voltage characteristics, and the needle stuck phenomenon, and it is possible to reduce the mechanical hysteresis of the cross-coil type instrument unit.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a cross coil type instrument according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific configuration of a constant power supply circuit.

FIG. 3 is a timing chart of each signal.

FIG. 4 is a flow chart for explaining the operation of the embodiment.

FIG. 5 is a circuit configuration diagram of a conventional cross coil type instrument.

6 is a signal waveform diagram of each part of the circuit configuration shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 F / V conversion circuit 2 Signal processing circuit 3 Drive circuit 4 Crossing coil type instrument unit 21, 22 Waveform generation circuit 31, 32 Pair of coils 33 Movable magnet

Claims (1)

[Claims for utility model registration] 1. A movable magnet (33) which is magnetized by two poles under the magnetic action of a pair of coils (31), (32) which are arranged to intersect each other at a predetermined angle. ) Is rotatably disposed, and a cross coil type instrument unit (3) and two waveform generating circuits (21) and (22) for inputting signals that change according to the measured quantity Drive signals (b) that have a predetermined phase difference from each other and that change according to the values of the signals by performing signal processing by
In a cross-coil type instrument provided with a drive circuit (3) for outputting (c) and a constant voltage circuit (7) for supplying power to the drive circuit, from the constant voltage circuit (7) to the drive circuit (3) The cross-coil type meter is characterized in that the power supply voltage is set to periodically switch to a low voltage.